There are 'Friends,' and there are Friends. Here's how one innovative company created its own rate-of-engagement score to keep track of online user-engagement.

<strong>Extreme engagement</strong>: When GoPro, the fast-growing company that makes the HD video camera beloved by extreme-sports enthusiastsâ€”such as the amateur videographer diving hereâ€”wanted to better understand its fans online, it created its own metric for doing so.Courtesy Company